Kruskal's Algorithm

Graph/Kruskal.cpp

@@ -0,0 +1,92 @@
+#include "bits/stdc++.h"
+//#include <boost/multiprecision/cpp_int.hpp>
+//using namespace boost::multiprecision;
+const int mx = 1e6+5;
+const long int inf = 2e9;
+typedef long long ll;
+#define rep(i,n) for(i=0;i<n;i++)
+#define repp(i,a,b) for(i=a;i<=b;i++)
+#define pii pair<int,int>
+#define vpii vector< pii >
+#define vi vector<int>
+#define vll vector<ll>			
+#define r(x) scanf("%d",&x)
+#define rs(s) scanf("%s",s)
+#define gc getchar_unlocked
+#define pc putchar_unlocked
+#define mp make_pair
+#define pb push_back 
+#define lb lower_bound
+#define ub upper_bound
+#define endl "\n"
+#define fast ios_base::sync_with_stdio(false);	cin.tie(NULL);	cout.tie(NULL);
+using namespace std;
+void in(int &x)
+{
+    register int c = gc(); x = 0; int neg = 0;
+    for(;((c<48 || c>57) && c != '-');c = gc());if(c=='-') {neg=1;c=gc();} for(;c>47 && c<58;c = gc()) {x = (x<<1) + (x<<3) + c - 48;}
+    if(neg) x=-x;
+}
+void out (int n) { int N = n, rev, count = 0;rev = N;  if (N == 0) { pc('0');  return ;}   while ((rev % 10) == 0) { count++; rev /= 10;}  rev = 0;while (N != 0) { rev = (rev<<3) + (rev<<1) + N % 10; N /= 10;}while (rev != 0) { pc(rev % 10 + '0'); rev /= 10;}
+while (count--) pc('0');
+}
+ll parent[mx],arr[mx],node,edge;
+vector<pair<ll,pair<ll,ll>>>v;
+void initial()
+{
+	int i;
+	rep(i,node+edge)
+		parent[i] = i;
+}
+int root(int i)
+{
+	while(parent[i] != i)
+	{
+		parent[i] = parent[parent[i]];
+		i = parent[i];
+	}
+	return i;
+}
+void join(int x,int y)
+{
+	int root_x = root(x);						//Disjoint set union by rank
+	int root_y = root(y);
+	parent[root_x] = root_y;
+}
+ll kruskal()
+{
+	ll mincost=0,i,x,y;
+	rep(i,edge)
+	{
+		x = v[i].second.first;
+		y = v[i].second.second;
+		if(root(x) != root(y))
+		{
+			mincost += v[i].first;
+			join(x,y);
+		}
+	}
+	return mincost;
+}
+int main(){
+	fast;
+	while(1)
+	{
+		int i,j,from,to,cost,totalcost=0;
+		cin>>node>>edge;					//Enter the nodes and edges
+		if(node==0 && edge==0)	break;				//Enter 0 0 to break out
+		initial();						//Initialise the parent array
+		rep(i,edge)						
+		{
+			cin>>from>>to>>cost;				
+			v.pb(mp(cost,mp(from,to)));
+			totalcost += cost;
+		}
+		sort(v.begin(),v.end());
+		// rep(i,v.size())
+		// 	cout<<v[i].first<<"  ";
+		cout<<kruskal()<<endl;
+		v.clear();
+	}
+	return 0;
+}